BasicPathUsageException：无法加入基本类型的属性

Question

I am using Java 8 with JPA (Hibernate 5.2.1). I have a like clause which works perfectly, until I introduce the like clause to make use the foreign key table values too.

I am getting the following error:

BasicPathUsageException: Cannot join to attribute of basic type

I think the problem is related to the fact that I have a join table, and I am not sure how to create the LIKE Join using the join table.

Employee - employee_category - category

model (Employee.java):

@ManyToMany(cascade = CascadeType.ALL, fetch=FetchType.EAGER)
@JoinTable
(
    name="employee_category",
    joinColumns={ @JoinColumn(name="EMP_ID", referencedColumnName="ID") },
    inverseJoinColumns={ @JoinColumn(name="CAT_ID", referencedColumnName="ID") }
)
private Set<Category> categories;

model (Category.java):

@Id
private String id;

JPA

When I introduce the following code, it fails with the error above (I think the problem is with this new piece of code):

Join<T, Category> category = from.join("id");
predicates.add(criteriaBuilder.like(category.<String>get("name"), "%" + searchQuery + "%"));

This is the entire method:

protected List<T> findAllCriteria(String[] orderByAsc, String[] orderByDesc, Class<T> typeParameterClass,
        int firstResult, int maxResults, String searchQuery) {
    CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder();
    CriteriaQuery<T> criteriaQuery = criteriaBuilder.createQuery(typeParameterClass);

    // from
    Root<T> from = criteriaQuery.from(typeParameterClass);
    criteriaQuery.select(from);

    // like
    if (searchQuery != null && searchQuery.trim().length() > 0) {

        List<Predicate> predicates = new ArrayList<Predicate>();
        for (String name : getColumnNames(typeParameterClass)) {
            Predicate condition = criteriaBuilder.like(from.<String>get(name), "%" + searchQuery + "%");
            predicates.add(condition);
        }
        Join<T, Category> category = from.join("id");
        predicates.add(criteriaBuilder.like(category.<String>get("name"), "%" + searchQuery + "%"));

        criteriaQuery.where(criteriaBuilder.or(predicates.toArray(new Predicate[] {})));
    }

    List<T> results = (List<T>) entityManager.createQuery(criteriaQuery).setFirstResult(firstResult)
            .setMaxResults(maxResults).getResultList();
    return results;
}

Any help will be appreciated.

Answer 1

求助：加入category = from.join（“categories”）;